Bigger Brains Come With A Price

A new study on brain size published today in the journal Current Biology supports the idea that bigger brains make you smarter, but may come at a cost.”The human brain only makes up 2 per cent of our total body mass but stands for 20 per cent of our total energy demand,” Niclas Kolm, an animal ecologist from Uppsala University in Sweden, said in a press release. “It is a remarkably costly organ energetically.”

In other words, having a larger brain can increase cognitive ability, but comes at a cost to other parts of the body because it requires more energy (A previous study suggested that cooking and eating meat could have made people smart because it provided humans with enough energy to support a larger brain).

“We provide the first experimental evidence that evolving a larger brain really is costly in terms of both gut investment and, more importantly, reproductive output,” Kolm said

In the study researchers selected guppies for large and small brain sizes. The guppies with larger brains had a 9 per cent larger brain than the small-brained guppies. They performed tests of numerical learning and the larger-brained female guppies significantly outperformed the female guppies with a smaller brain, but there was no difference in male guppies.

The difference in male and female cognitive abilities may be due to the female generally being more active and innovative while gathering food, which may have given the gender an advantage in the tests. Males guppies care about food less, which could explain why they did not perform well on the tests.

The guts from the guppies were also found to be 20 per cent smaller in larger-brained guppies and they had 19 per cent less offspring than their smaller brained counterparts.